SNA Services: Ensure IVTCSM ASSIGN_BUFFER requests do not exceed 500 images for a single CSM buffer

Description: Beginning with z/OS V1R13, Communications Storage Manager (CSM) will reject the ASSIGN_BUFFER request after 500 image buffers of a single CSM buffer are requested, and CSM will return a new reason code of 26. The new reason code 26 states: "Assign buffer request failed because CSM reached the limit of the maximum number of image buffers of the single CSM buffer."

Element or feature:

Communications Server.

When change was introduced:

z/OS V1R13.

Applies to migration from:

z/OS V1R12.

Timing:

Before installing z/OS V2R1.

Is the migration action required?

No, but recommended. Your application probably does not request more than 500 images of a CSM buffer; however, you should examine IVTCSM ASSIGN_BUFFER calls to ensure that this is the case.

Target system hardware requirements:

None.

Target system software requirements:

None.

Other system (coexistence or fallback) requirements:

None.

Restrictions:

None.

System impacts:

None.

Related IBM Health Checker for z/OS check:

None.

Steps to take: To prevent application failures due to excessive ASSIGN_BUFFER requests:

Identify any authorized applications that use CSM services and verify that the number of image buffers requested by IVTCSM ASSIGN_BUFFER for a single CSM buffer can never be more than 500.
If necessary, change the application so the total number of IVTCSM ASSIGN_BUFFER image buffer requests is 500 or less.

Reference information: None.